Unlicensed mobile access (UMA) technology provides a link between GSM/GPRS cellular networks and IP-based wireless access networks. This link enables a cellular provider to offer the same voice and data services regardless of whether the services are delivered by a cellular base station or an IP network. Built-in handover mechanisms and mobility management features make it possible to transition between the two access methods without interrupting service.
In a typical implementation, a UMA network controller (UNC) passes voice and data signals between a mobile station and the core cellular network. The UNC receives UMA packets from the mobile station over an IP network, converts them into a suitable format, and directs them to the core cellular network. The core cellular network receives voice traffic at a standard A-interface and data traffic at a standard Gb-interface. In the other direction, the cellular core signals the UNC at its interfaces, the UNC converts these signals into packets, and the UNC sends the packets to the mobile station over the IP network. The entire process is transparent to both the mobile station and the cellular core. From the mobile station's perspective, the wireless network is simply an additional radio resource. IP-specific functionality is abstracted from the higher level service and control logic. The core cellular network, on the other hand, interacts with the UNC as if it was a conventional base station. At a high level, the UMA network functions as a single cell within the larger cellular network.
The UNC participates in a process of authentication whereby the mobile station is granted access to the core cellular network. As a part of this process, the mobile station contacts the UNC at an address on the IP network. The UNC contacted may or may not be the UNC that serves the geographic area in which the mobile station is located. A mobile station may contact multiple UNCs before locating the serving UNC and becoming registered as part of the UMA network. A security gateway at the serving UNC employs a challenge-response mechanism to authenticate the mobile station. As part of this process, the mobile station exchanges encrypted communications with the core cellular network. The encrypted communications contain information derived from a subscriber identity module (SIM) located within the mobile station. When authentication is successfully completed, the serving UNC provides system information to the mobile station so that its availability at the UMA network cell can be registered with the core cellular network.
After registration is complete, signaling and bearer traffic flow between the mobile station and the serving UNC through an IPsec (IP Security) tunnel When the mobile station wishes to place a call, for example, it sends UMA packets to the serving UNC requesting a connection. The serving UNC notifies a mobile switching center (MSC) in the core cellular network. The MSC then directs the serving UNC to create a voice path from the mobile station to a voice port on its A-interface. The serving UNC responds by creating a Voice over IP (VoIP) bearer path to the mobile station. Audio is transported back and forth across the IP network as a VoIP data flow on the bearer path. When the serving UNC receives audio data from the mobile station, it is transcoded and directed to a voice port at the A-interface. Similarly, when the serving UNC receives audio data from the MSC, it is transcoded and sent to the mobile station over the bearer path. All communications are passed through the IPsec tunnel for security.
GPRS data services are also available on the UMA network. When a mobile station wishes to access these services, it creates a transport channel to the serving UNC. The transport channel carries GPRS payload packets between the mobile station and the serving UNC. The serving UNC forwards payload packets received from the mobile station to a serving GPRS support node (SGSN) through its Gb interface. In like manner, the serving UNC receives GPRS packets from the SGSN and forwards them to the mobile station over the transport channel.
FIG. 1 illustrates the operation of a conventional UMA communication system. UMA communication system 100 is shown as including, in part, mobile stations 108, 110 and local area network (LAN) 104. LAN 104 includes workstations 116, 117 and application server 118. An internet connection 120 is also provided. Mobile stations 108, 110 connect to LAN 104 through a wireless access point 112.
When mobile station 108 wishes to place a UMA call, for example, it connects to LAN 104 and begins a process of authentication with the core cellular network through a serving UNC 124. This process results in formation of a secure tunnel between the devices. At this point, mobile station 108 communicates with serving UNC 124 by sending and receiving UMA packets through the secure tunnel. These packets represent GSM/GPRS signaling and bearer traffic. Depending upon the type of communication, serving UNC 124 relays packet data either to MSC 128 or SGSN 132 where it is presented to the core cellular network. Return communications follow the same path from the core cellular network to the mobile station.
As shown and described, conventional UMA communication system 100 neglects the resources and functionality of local area network 104. Regardless of caller/callee, all voice communications follow a path from sender, across the internet, to the UNC, and back down to the recipient. This is true even if both devices are connected to the same local area network. Thus, if mobile station 108 wishes to call mobile station 110, audio data from mobile station 108 will be transmitted to the local area network 104, traverse the internet 120, and be received at serving UNC 124. Serving UNC 124 will return the audio data over the internet 120 to the local area network 104 where it will ultimately be received by mobile station 110. This process uses network bandwidth inefficiently, introduces delay into UMA voice calls, and potentially degrades call quality.
In addition, by neglecting LAN resources, UMA devices in a conventional system are not able to communicate efficiently with other LAN-based communication devices. For example, a LAN may support interoperability among numerous SIP, H.323, and TDM based communication devices through one or more media gateways. UMA devices do not benefit from this shared connection. As described, UMA communications always traverse the internet before reaching their intended recipients. Thus, there is a need in the art for a LAN-centric approach to UMA communications. It is therefore an object of the present invention to promote efficient voice and data communications for UMA-enabled devices connected to the same local area network. It is also an object of the present invention to promote efficient communication between UMA and non-UMA communication devices when these devices are connected to the same local area network.